Small-World Network Analysis of Cortical Connectivity in Chronic Fatigue Syndrome Using Quantitative EEG

Abstract

The aim of this study was to explore the relationship between complex brain networks in people with Chronic Fatigue Syndrome (CFS) and neurocognitive impairment. Quantitative EEG (qEEG) recordings were taken from 14 people with CFS and 15 healthy controls (HCs) during an eye-closed resting condition. Exact low resolution electromagnetic tomography (eLORETA) was used to estimate cortical sources and perform a functional connectivity analysis. The graph theory approach was used to characterize network representations for each participant and derive the "small-worldness" index, a measure of the overall homeostatic balance between local and long-distance connectedness. Results showed that small-worldness for the delta band was significantly lower for patients with CFS compared to HCs. In addition, delta small-worldness was negatively associated with neurocognitive impairment scores on the DePaul Symptom Questionnaire (DSQ). Finally, delta small-worldness indicated a greater risk of complex brain network inefficiency for the CFS group. These results suggest that CFS pathology may be functionally disruptive to small-world networks. In turn, small-world characteristics might serve as a neurophysiological indicator for confirming a biological basis of cognitive symptoms, treatment outcome, and neurophysiological status of people with CFS.

A systematic review of neurological impairments in myalgic encephalomyelitis/ chronic fatigue syndrome using neuroimaging techniques

“…Females made up the largest proportion of participants. There were only 10 studies which reported race, where majority of the participants were Caucasian [12,19,21,26,27,37,41,47,48,52]. Mean age across all studies was 40.9 years for ME/CFS patients and 39.07 years for HCs.…”

“…In all twin studies, levels of zygosity were assessed and ascertained at 99.9% [12,21,27]. 47 of the 55 identified papers included participants that fulfilled the requirements of being diagnosed with the Fukuda criteria [12,14,[16][17][18][19][21][22][23][24][25][26][27][28]30,31,[34][35][36][37][38][39][40][41][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. Three of the papers used the more stringent CCC criteria to classify ME/CFS patients [15,29,42].…”

“…There were four different neuroimaging techniques used to assess neural changes in ME/ CFS compared with HCs. Out of the 55 studies: 16 studies utilised MRI [11,[13][14][15]20,[31][32][33][34][35][36]43,53,58,62,63], 17 used functional MRI (fMRI) [16,18,[21][22][23][24]26,34,[40][41][42][43]45,49,[49][50][51], five used PET scans [17,25,28,30,44] and 11 used EEG [12,27,29,38,39,[46][47][48]54,55]. The remaining studies used magnetic resonance spectrometry (MRS) [19,…”

“…Nine articles discussed significant changes in energy waves using EEG [12,27,29,37,38,[46][47][48]55]. These articles include the three previously mentioned papers that discussed EEG electrical activity in relation to sleep [12,37,55].…”

The Development of the DePaul Symptom Questionnaire: Original, Expanded, Brief, and Pediatric Versions

“…The DSQ-1 has been used for a variety of purposes, including documenting specific ME and CFS vision-related abnormalities ( 27 ). In addition, using QEEG recordings, Zinn et al ( 28 ) estimated cortical sources and perform a functional connectivity analysis on 84 Brodmann areas representing the entire cortex. Neurocognitive impairment, as measured by the DSQ-1's cognitive composite score, was negatively associated with small-worldness index for the delta band under observation.…”